1. Field of the Invention
This invention relates to an image pickup system and an image pickup apparatus arranged to be capable of transferring a large amount of picked-up image data at a high speed with simple arrangement.
2. Description of the Related Art
FIG. 6 is a block diagram showing the arrangement of the conventional image pickup system. The conventional image pickup system is composed of an image pickup apparatus 101, a video input card 201 and a personal computer (hereinafter referred to as PC) 102. A video image picked up by the image pickup apparatus 101 is displayed at the PC 102. Transfer between the image pickup apparatus 101 and the video input card 201 is conducted in analog signals. The video input card 201 is connected to the PC 102 by a digital interface (hereinafter referred to as I/F) part 112. In picking up an image, these parts operate as described below.
In the image pickup apparatus 101, a control part 202 supplies synchronizing and driving signals to a timing generator 111 and a video signal generating part 106 at the time of video shooting. The timing generator 111 then forms signals for driving a CCD 104 and an A/D (analog-to-digital) converting part 105 on the basis of the signals from the control part 202.
When an image of an object of shooting is formed on the CCD 104 through an optical system 103, the image is converted into a digital signal by the CCD 104 and the A/D conversion part 105. The digital signal is sent to a video signal generating part 106, which adjusts the digital signal into a video signal. The adjustment includes gain (AE) adjustment and white balance (AWB) adjustment which are carried out in a known manner.
The digital video signal thus formed by the video signal generating part 106 is sent to an encoding-and-D/A part 203 to be converted into an analog video signal conforming to the NTSC system. The analog video signal is sent to the video input card 201.
In the video input card 201, the analog video signal is first converted into digital luminance and color-difference signals by an A/D-and-decoding part 204. The luminance and color-difference signals are supplied to a matrix computing part 205 to be converted into R, G and B signals each of which consists of 8 bits. The R, G and B signals are stored in a frame memory 206 as a video signal.
The video signal stored in the frame memory 206 is read out according to a reading signal coming from the PC 102 which is connected to the video input card 201 via an I/F part 112. The video signal is sent to the PC 102 through the I/F part 112. Each part of the video input card 201 is controlled by a video signal control part 207.
The video signal is taken into the PC 102 by operating a program 208 which is provided on the PC 102. When an instruction is given from the program 208 to read a video image, an operating system 113 sends a reading signal to the video input card 201 through the I/F part 112. As a result, the video signal comes to be recorded on a memory (not shown) which is disposed within the PC 102. The input video signal has each picture element thereof composed of a total of 24 bits including 8 bits for each of colors R, G and B. When video image data for one picture has been inputted, the program 208 converts a color space of the video image according to the capability of a display part 115.
In a case where, for example, the display capability of the display part 115 indicates 16 bits of color, the program 208 thins the picture element value of 24 bits on the memory down to 15 bits, i.e., five bits for each of the colors R, G and B and records the thus-thinned video signal on the memory again. If the display capability of the display part 115 indicates 8 bits of color, the program 208 looks up the video image data on the memory to create optimum conversion pallet data for 8 bits. The conversion pallet data is sent via the operating system 113 to the display part 115 to match the color space.
The program 208 converts the value of each picture element on the memory on the basis of the above-stated conversion pallet data. Upon completion of conversion of data for one picture, the program 208 sends the data to the display part 115 via the operating system 113 so as to have the picked-up video image displayed there.
In order to send the picked-up video image in a digital form to the displaying PC without changing the digital form, the conventional image pickup system or the image pickup apparatus necessitates use of a high speed I/F and a high speed CPU. Accordingly, some trouble, such as a frame dropout or the like, might take place in the stage of displaying a picked-up moving image, depending on the processing capability of the system as a whole. In such a case, it is hardly possible to fully utilize the moving-image processing capability of the image pickup apparatus. Further, in a case where an analog I/F is employed for a higher processing speed, it has been hardly possible to avoid a deterioration in picture quality due to a noise.